extend structure of package selection to support selection by version

the current package selection structure only supports selecting one package with all versions at a time. add a new map to track the selected versions per selected package. detect package selection with the old map (i.e. package x selected == true or false) and track versions per package in the new map (package x versions = {...})

i decided against just one structure with a map to track all versions because i want to:
select all package versions with a click on the package followed by selecting just one version by clicking on that version; the datastructure must support having a default of select-all versions and a specific one where the user selects a number of versions explicitly. it's trickier to implement all checks without too much overhead for angular, so i decided for 2 stuctures instead

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
add hover animation to version fields separate from package field

i.e. when hovering over a package summary, the color is slightly lighter than when hovering over its version elements. the versions cannot be styled separately as of right now because the :hover selector in css can't style the parent element. javascript is the proper way to solve this, but slightly overkill for this first version. it may be adjusted later on, to only style the version fields when it's hovered over and not the parent field...

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
improvement: restyled node and package selection items to support subselection

this is important for version selection of packages: hover over child elements to only animate gives the freedom to only animate the child (as done here) or both child and parent. also adjusted the node scss to since package and node list both use the same styling, but they look and behave slightly differently: for node list the user always selects only the node element as a whole, while for packages the user either selects the package (ie. all versions of that package) or a number of versions of a package he is interested in

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
feature: only select specific package versions in frontend

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
add test to see if all versions of a package get pulled into the selection

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
add test to see if a specific version of a package gets pulled into the selection

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
update showPackage to only show the package details if it is selected

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
fix linter issues

Signed-off-by: Dominik Richter <dominik.richter@gmail.com>
Merge pull request #33 from TelekomCloud/select-package-version

Well done.